1. Field of the Invention
The present invention relates to an antitheft device which protects commodities for rent or sale put in individual cases, such as audio or visual CDs and video tapes and game software, from being removed from the cases and out of a shop without permission, and which also protects the cases from being pried open by applying an excessive force thereto in an opening direction. The invention also relates to a case equipped with such a device.
2. Prior Art
In rental shops, as is well known, displaying rental commodities put in individual cases might stimulate some customers to steal them because of absence of measures to protect the cases from being opened.
Therefore, to prevent thefts, empty cases are displayed in a shop and when a Q customer brings an empty case to the counter, a clerk fetches a corresponding commodity from a storage place and rents it to him/her.
Adopting this system can protect rental commodities from being stolen because customers never have a chance of touching the commodities directly.
However, it is extremely troublesome for the clerk to locate rental commodities requested by the customer in the storage place and to keep the storage place well-ordered, which causes various problems such as hindering a smooth rental process and demanding a large storage place.
These problems could be solved by displaying rental commodities put in individual cases in a shop and making a customer take a desired rental commodity out of a case and bring it to the counter for a rental process.
However, this system might stimulate some customers to take rental commodities out of the cases and out of the shop without permission because they can directly touch rental commodities.
Such stealing could be further encouraged by a simple structure of a case for storing a commodity consisting of a box and a lid without any measure to prevent opening of the lid.
To prevent thefts, each rental commodity is attached with an antitheft tag in an arbitrary position, with the tag having a unique ID code without a main power supply. A predetermined high-frequency electromagnetic field is provided at a gate of a shop. When a customer leaves the shop through the gate with a rental commodity, a resonance circuit of the ID code resonates to transmit the unique ID code and detects a modulation of the high-frequency electromagnetic field so as to detect passing of the rental commodity. A clerk monitors whether the commodity is rented or removed without permission.
However, there is an inconvenience in that unless the ID code (tag) is shielded by any method during a rental process at the counter, commodities rented according to a predetermined procedure are also detected as having been removed without permission.
This requires a troublesome shielding process, and various goods necessary for shielding greatly increase cost.
The aforementioned problems are not restricted to rental commodities but hold true to various kinds of commodities for sale such as clothes, accessories, and daily necessities when they are attached with a tag to be protected from being stolen.
In order to solve these problems, Japanese Laid-open Patent Publication No. 2002-080086 (Publication date: Mar. 19, 2002) discloses an antitheft device in which a key member is designed to be inserted into a through hole formed on peripheral walls of a box and lid, of a case, which overlap each other on inner and outer peripheral edges of the box and the lid when the case is closed, and this inserted key member prevents the case from being opened and a commodity thereinside from being removed from the case.
The key member is attached with an antitheft tag for protecting the commodity from being removed from a shop with the case.
On a surface where the key member and the case oppose each other is provided a locking member which is pressed back when the key member is inserted and brought into an engagement relationship with the key member when insertion of the key member is completed. The engagement relationship between the locking member and the key member prevents the key member from being pulled out.
It goes without saying that release of the engagement relationship is performed by inserting a releasing tool of the shop and by pulling out the key member with the releasing tool.
In the antitheft device of this type, the surface where the inserted key member and the through hole of the case oppose each other forms a straight line.
This allows something with a flat tip such as a screw driver to be forced between straight surfaces and to be twisted until the case is damaged, or allows the screw driver tip to be pressed strongly onto the key member in a releasing direction.
The driver tip may damage the locking member in the engagement relationship with the key member, or release the engagement relationship.
This structure is responsible for theft of commodities put in cases.
Even a case shown in FIG. 9, which is composed of a box and a lid and is provided with a temporary locking member to prevent the lid from being opened, peripheral walls of the box and the lid are directly butted with each other, thereby allowing a tip of a screw driver to be forced into between these directly butted edges.
This allows the case to be opened by twisting the driver.
When a case composed of a box 101, a lid 102, and appropriate hinges is in a closed condition, an inner peripheral wall 103 of the box 101 and an outer peripheral wall 104 of the lid 102 overlap with each other inside and outside as shown in FIG. 22, and if an external pressure is applied to the box 101 and the lid 102 in a direction indicated by arrows shown in FIG. 23, then there is a phenomenon that the outer peripheral wall 104 bends outwardly.
This phenomenon becomes more serious as the external pressure is stronger.
As a result, a finger tip or a driver can be easily forced into a space formed inside the outer peripheral wall, thereby further bending the outer peripheral wall outwardly to finally open the case.
The case could be forcibly opened by pressing a finger tip into between the outer and inner peripheral walls after an external peripheral wall is bent outwardly, and by hooking this pressed finger tip on an open edge of an outer or inner peripheral wall and pulling it out.